Antiplatelet aggregation and cytotoxicity of BA from M. bracteata and its acetyl derivative

Abstract

Jonty Swanepoel, Hendrik Marck and Ernie Verwoerd

Platelet dysfunctions are implicated in cardiovascular diseases. Management of abnormal platelet aggregations with natural products is a promising approach to the treatment of cardiovascular diseases. In this study, betulinic acid (BA) isolated from Melaleuca bracteata leaf extract, and its acetyl derivative (3-β acetylbetulinic acid) (BAA) were investigated for their antiplatelet aggregation and cytotoxic activity. Structures of the compounds were established and confirmed through spectral (nuclear magnetic resonance [NMR], infrared [IR], mass spectroscopy [MS]) data analysis. The antiplatelet aggregation activity of the compounds was separately evaluated on collagen, adenosine diphosphate [ADP], thrombin and epinephrine induced rat platelet aggregations. The 3-(4,5)- dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) cytotoxicity assay was used to determine the cytotoxic effect of the compounds against human embryonic kidney (HEK293) and hepatocellular carcinoma (HEPG2) cell lines. The triterpenoids exhibited significant (p<0.05) dose dependent antiplatelet aggregation activity. The highest inhibitory activity of BA and BAA was observed on epinephrine induced platelet aggregation with IC50 values 0.78 and 0.85 mg/ml, respectively. BA and BAA showed less cytotoxicity effect on both HEK293 cell (IC50 1027 and 1051 µg/ml, respectively) and HEPG2 cells (IC50 448 and 672 mg/ml, respectively). The results suggest that the compounds could serve as potential templates for synthesis of new antiplatelet drugs.